1. Field of the Invention
This invention relates to the field of generating and executing applications for computer systems.
2. Background Art
Computer systems utilize one or more microprocessors as the central processing unit (CPU) to execute instructions and control operations of the computer system. The microprocessor receives data and instructions from an associated main memory and performs operations based on those data and instructions. There are a number of microprocessors that are used as the central processing unit of a computer system. The terms "computer architecture", "environment", "hardware", and "platform" of a computer system refer to the microprocessor type used in the computer system.
One class of microprocessors, manufactured by Motorola, are referred to as "68K" type microprocessors. This class of microprocessor includes such microprocessors as the 68000, 68020, 68030, and 68040 microprocessors. Another type of microprocessor is manufactured by Intel, AMD, and others, and is known as "i86" type microprocessors. These include the 286, 386, 486, pentium, etc. Other processors, known as reduced instruction set microprocessors ("RISC" microprocessors), are also used in computer systems.
Computer systems execute instructions provided by application programs. An application program is a collection of instructions that, when executed, perform tasks and provide functionality to a computer system. An example of an application program is a word processing program. A word processing program is used to create and edit documents and files.
Presently, application programs such as word processing programs, spreadsheets, databases, etc., must be generated with a specific microprocessor or architecture in mind. Providing a spreadsheet program that operates on the above-mentioned three microprocessor types requires that at least three versions of the spreadsheet program be generated: one for 68K architectures; one for i86 architectures; and one for RISC architectures.
In addition, within each family of microprocessors, individually tailored code may be required. For example, i86 microprocessors include "SX" types that do not have math coprocessors, and "DX" types that do include math coprocessors. An application program may be optimized for one type of microprocessors and may be incompatible with the other.
Although the object code of an application program varies with each architecture (and CPU type within an microprocessor family), often the application programs are derived from the same source code. Source code is written in a high level language that is translated by a compiler or interpreter into machine code for operation on a computer. A compiler is a program that converts a program written in a high-level language into either machine code or assembly language, holding the instructions in memory without executing them. The compiled program is then transferred to storage disks for execution at a later time. For example, application programs are often compiled and stored on "floppy" disks or CD-ROM disks for distribution.
Referring to FIGS. 1A-1C, three versions of an application program are illustrated. In FIG. 1A, an executable applicaticon program is illustrated as comprising object code 101. The object code 101 is derived from source code that has been translated by a compiler into object code executable on an i86 computer system. FIG. 1B illustrates an application program for execution on a 68K-type computer system. FIG. 1C illustrates source code that has been compiled into object code for RISC-type computer systems. Each of the files in FIGS. 1A-1C is a separate file and requires its own directory listing when loaded onto a computer system.
A disadvantage of writing application programs for a plurality of architectures is the requirement that the application programs be distributed individually. That is, the application program for each architecture is considered to be a separate product and a separate disk must be provided for each. When purchasing the application program, the purchaser must review the product and select the version that is appropriate for the purchasers computer system. For example, if the purchaser has a computer system based on the 386SX microprocessor, the purchaser must select a version of the application program that is designed for that architecture.
Another disadvantage occurs when an application program is shared on a network comprised of computers of different architectures. If computers of three different architecture types are connected to the network, at least three different versions of the application program must be stored on the network. In addition, each user must select the appropriate version of the application for use.
One prior art attempt to provide a method for providing a single application for a variety of architectures and formats is the ANDF system, developed by OSF. This is an architecture neutral binary format. A disadvantage of this scheme is that it requires conversion to the native architecture at installation time.